System for electrical distribution.



P. H. THOMAS.

SYSTEM OF ELECTRICAL DISTRIBUTION.

APPLICATION FILED MAR. 29- I913- Patented May1,1917.

SHEETS-SHEET l- P. H. THOMAS.

SYSTEM OF ELECTRICAL msmmunow.

APPLICATION FILED MAR-29. 1913.

fim MC um 'P. H. THOMAS.

SYSTEM OF ELECTRICAL DISTRIBUTION. APPLICATION FILED MAR. 29. I913.

4 SHEEN-SHEET 4.

I J W awpe/wro'c Patented May I, 1917.

PATENT OFFICE.

UNITED STATES PERCY H. THOMAS, or UPPER MQNTCLAIR, NEW JERSEY, ASSIGNOR To COOPER HEWITT ELECTRIC 00., or HOBOKEN, NEW JERSEY, AconroRATIoN on NEW JERSEY.

SYSTEM OF ELECTRICAL DISTRIBUTION.

Application filed March 29, 1913. Serial No. 757,499.

To all whom it may concern:

Be it known that I, PERCY I-I. THOMAS, a citizen of the United States, and resident of Upper Montclair, county of Essex. State of New Jersey, have invented certain new and useful Improvements in Systems of Electrical Distribution, of which the following is a specification.

My invention relates to the electrical transmission and utilization of power and more particularly to the use of high voltage .direct current for this purpose; Systemsare already in use in which high voltage direct currents are generated, transmitted and utilized,.but these systems are limited in application by the fact that a number of direct current synchronous machines must be used in series where voltages are high and are further limited by the fact that the frames and shaft couplings of these series machines must be insulated. I have devised a scheme by which power can be transmitted over very high voltage lines in the form of direct current and conveniently utilized without the use of such series coupled synchronous machines. Briefly I make use of an alternating generating system producing high alternating voltages suitable for transmission purposes and rectify these alternating voltages through mercury vapor rectifiers for supplying the actual transmission line. At the receiving point or points for the purpose of receiving and distributing the energy transmitted I also provide an alternating potential machine capable of producing, with the aid of transformers, if necessary, high alternating voltages commensurate I Withthe voltages of the line. Through the use of additional mercury vapor rectifiers and certain switch cylinders which I have devised I apply the direct current. from the line upon the alternating electromotive force at the receiving point in a manner to be hereinafter explained and thus furnish power thereto. To enable an alternating generator to receive power from my direct current transmission line I rely funda mentally on the fact now well known that a superior 'electromotive force' when producing a flow of current against a'counter directed electromotive force supplies power to the circuit of the inferior electromotive force.

In carrying out this invention it is necessary to apply the direct current from the line upon the alternating current circuits at the receiving end at such times and in such directions that the actual flow of current is always in the direction of the line voltage and against the receiving alternating. electromotive force; that is, in any one circuit Patented Ma .1, 191 7.

connecting the two electromotive forces current can be permitted to flow only during one half of a cycle. and further only during that half in which thedirect current voltage is opposed to that of the alternating current. 'I utilize vapor electric rectifiers connected between the direct current line and the alternating receiving circuits to accomplish the suppression of the current flow during the periods of wrongly directed electromoti've force. 'But it is further desirable in the economical use of my system to sup press the flow of current in the periods'when the electromotive force is properly directed, should the current become reversed through the rising of the alternating potential above the direct current line potential.

Considering a single wave of the alter nating electromotiveforce and assuming the line voltage to be introducedin the same cirrent due to the electromotive force, it will be clear that the direct current voltage will be superior in magnitude at the beginning of the cycle and that a considerable current will tend to flow against the alternating voltage. As the wave proceeds, however, while the direct voltage remains constant the alternating voltage increases tending to reduce the amount of current flowing and as the alternating voltage rises still more, a point will be reached (assuming the alternating wave of suflicient maximum peak) at which the two electromotive forces will be equal and. current will tend to cease to flow for the moment. As, however, the wave proceeds stillifurther, the alternating electromotive force becomes the superior and current will tend to flow in the reverse direction from the alternating to the direct current circuits.- This I prevent by inserting between the direct current and alternating current systems a mercury vapor rectifier so polarized as to permit the flow of current in the desired direction only; so that when the current flowing from the direct to the alternating circuits once ceases as above pointed out the tendency for the reversal of flow will be withstood.

Passing now. to the next wave of electromotive force in which the direct current potential remains unchanged but the alternating current Wave is reversed in direction, I interrupt the continuity of the circuit be tween the systems at some period after the ceasing of current flow between the two circuits and before the'return of the tendency for the current to flow again in the original direction due to the drop in the peak of the portunity would be provided for its sup-- pression.

It will be clear from what has been said that the principles involved in this invention, as far as this particular aspect is concerned, depend upon the presence of such an alternating current way in the receiving circuit as will rise super'or to .the direct current line potential near the peak so that the flow of current can be automatically cut off at the critical time. It is very important, however, that there be some means for adjusting, to the demands of the receiving circuit, the actual energy delivered. For example, should a receiving circuit be supplying a large demand and the voltages of the line'and the alternating machine be relatively adjusted to produce this result and should the load be suddenly removed, it is desirable that the system automatically reduce the absorption of power from the line corresponding to the amount of energy withdrawn. This may be accomplished in various ways, some of which I have illustrated in the drawings of the present application. For example, if on the withdrawal of power, the voltage of the receiving machine automatically increases it will lessen the period during which favorably directed current flows from the line and thus reduce the energy delivered to the system.

A high tension direct current transmission will require a continuous current,

which changesonly slowly, relatively speakmg, on account of the naturally high inductances in such a c1rcu1t;. but the flow of useful current from the line at the receiving end as so far provided for in the above explanation covers only intermittent cur rent flow and thus does not satisfy the natural characteristic of the supply. In the practical application, however, I utilize a plurality of connecting points between the line and the receiving circuit in such a manner that current can flow at any instant in some one of the several branch circuits. This plan is facilitated by the use of a polyphasc alternating machine at the receiving end such, for example, as a three phase machine. This will be more clearly understood by reference to the more detailed systems illus trated in the drawings and described hereinafter.

It will be seen from what has been said that the alternating machine at the receiving end acts as a sort of magnetizing or pilot machine to establish the frequency of the receiving circuit and to determine the wave form thereof and to act as a storage means for smoothing out the flow o'l cur; rent to the receiving circuits. The main flow of energy, however, will be from the direct current line wire to the transformers, where these are used. and out on the receiving mains directly, this energy fiow receiving the necessary modification and supplementation from the alternating current machine on the way.

In the drawings, Figure 1 represents a simple embodiment of the receiving system of my invention;

Fig. 2 shows a modification of the arrangement of rectifiers and synchronous cylinders;

Fig. 2 is a transverse section of cylinder A, showing the angular displacements of segments 1046*, 105 and 106 Fig. 2 is a transverse section of cylinder B, showing the angular displacements of segments 107", 108 and 109";

Fig. 3 shows a somewhat more complex but more eflicient and effective system for certain requirements;

Fig. 4 7 shows a generating system for producing high voltage direct current for the transmission line.

Fig. 5 shows the three electromotive force waves of a three phase circuit and the pertions thereof which are utilized for transfer of power. 3

Fig. 1 represents the circuits and apparatus at the receiving end of one embodiment of my power transmission system, 1 and 2 representing the incoming high tension direct current lines from the source. and 24, 25 and 26 representing the local feed wires. 27 represents a three phase machine connected to the three phase mains 24, 25 and 26, and 21, 22 and 23 are three delta-connected transformer secondary windings whose high tension windings are shown at 18, 19 and 20 respectively. The direct current: line voltage is impressed upon the three transformers through a number of multiple paths containing the rectifiers 5, 6, 7, 8, 9,10, 11, 12,

of a revolving cylinder, 3, provided with period of the revolution of the cylinder, 3,

any particular "circuit is closed. For example, the circuit of' the rectifier, '5, and the circuit of the rectifier, 8, are closed during the portion of the revolution indicated by the blocks marked and 35*. Similarly the circuits of the rectifiers '14 and15- are closed during a portion of the cycle correfsponding to shaded blocks 36 and 36 respectively and so on with the other circuits. I have called the element 27 in Fig. 1 a

synchronous machine meaning by this a machine which is always connected to thealternating current distribution mains and which in virtue of its momentum is at all times ready to supply for short periods alternating current and voltage of the normal generator type. Of course in this system the momentum of the machine 'is replenished by every current impulse from the direct current supply; In this sense, of course,

during the continuance of. the supply impulse the machine acts as a motor as well as acts as a generator. However, even during this period, thecmachine must support the flow of energy in one or more of the phases since the motor effect due to a passing supply impulse is not simultaneous in all the windings of the machine.

In actual operation it is understood that the cylinder, 3, rotates in synchronism with the machine, 27, as may be brought about,

for example, by a direct and rigid drive between the machine and the. cylinder. The cylinder may, however, lie/driven by a synchronous motor or otherwise to secure synchronism. As illustrated the cylinder, 3,

making one revolution for each complete period of the alternating supply, though, if desired, any number of, complete cycles might correspond to. a revolutionof the cylinder. For convenience I have illustrated in Fig. 5 one cycle of the three phase supply at the left ofthe development of the surface of the cylinder, 3; 32, 33 and 3% representing the three electromotive forces of the transformers 20, 19 and 18, respectively.

' An examination of the relative location of the several shaded blocks 35, 35 to 40, 40 inclusive makes it clear that one pair of circuits carries the whole current for a certain period; that then for a briefperiod an other pair of circuits operates in parallel with the first; that the first circuit is then interrupted permitting the second to operate for a definite period; that the third circuit is then put in parallel to the second for placed by the first circuit and so on cyclically. In other words, -the six double circuits take turns carrying the direct current from the line and there are brief transition periods during which current is leaving one pair of circuits and becoming established in another during which periods two pairs of circuits are'in parallel.

By an examination of the relation of the shaded blocks to the. electro-motive-forces of the transformersand remembering that the electromotive force, 32, Fig. 5, is the electromotive force of the transformer, 20; 33 the electromotive force of the transformer, 19; and34 of the transformer 18,'it is clear that the connection is completed in-one pair of circuits, 114, 114, for example, during thejtime that the electromotive force of the transformer winding 18 due to machine 27 connected with these circuits-is at or near its maximum .andfurther that when this maximum transformer electromotive force from machine 27 is in the one direction, the impulse of current from the positive main- 2* is made to pass through the rectifier 5 and transformer primary 18 in one direction and when the maximum electro-motive-forceis in the other direction the impulse of the current from the positive main 2 passes through the transformer primary 18 but through another set of rectifiers, 7 and 6, and in the opposite direction. More in detail the cir-' cuits may be traced as follows: With the apparatus in the position shown in Fig. 1 there is acurrent flow from the positive main over thebrush 35 and the segment 35 over the inductance 4, the rectifier 5, the inductance 17, the transformer primary 18, the rectifier 8, the inductance 4, the segment 35 to the'negative main. The cylinder 3 is so timed that, when the segments 35 and 35 are under the brushes'35 and 35 the counter electro-motive force of the synchronous machine produces a voltage in such a direction in the primary 18 as to be opposed in direction to the impulse from the positive main whose path was just traced, with the result that this impulse, which is of superior voltage, imparts energy to the synchronous machine 27 through the transformer windings 18, 21. At this particular instant no other segments are in such a po-, sition as to connect any pair of brushes. However, directly after the moment just considered the segments 40 and 40 are connected' to the corresponding brushes and current will flow from the positive main 2 over the segment 40", the inductance 4, the rectifier 11, the transformer primary 19, the inproduce an electromotive for in the primary 19 opposed to the direction of flow of the last described impulse from the positive main and energy is again imparted to the synchronous machine 27. At a slightly later time the segments 39 and 39 will come under their respective brushes and a circuit will be established from the positive mains throughthe rectifiers 13. and 16 and the transformer primary 20 as before and so on through the six circuits which cross the drum 3. In each case the impulse from the direct current sourceimparts a certain quantity of energy to the synchronous machine 27, these several disconnected energy portions being transmitted through the transformers in turn. As already explained the momentum of the synchronous machine 27 is sufficient to integrate the supply impulse and to support a substantially uniform rotation which maintains the normal alternating wave of voltage on the alternating current mains. In this it may be noted that the current impulses passing from the positive mains pass over the cylinder, through the rectifier to a transformer primary and back through an oppositely connected rectifier across the cylinder to the negative main. It will also be noted that when the circuit 115, 115 comes in parallel with the previously operating circuit 114, 114, that the alternating current electromotive force on the new circuit 115, 115 is less than that upon the old circuit 114, 114*, and since the alternating electromotive force is a counter electromotive force, the current will flow more readilyfrom the direct current line 2 in the circuit containing the lesser alternating current electromotive force, that is, the newly formed circuit 115, 115. Furthermore this will be to the exclusion of all current from the older circuit 114, 114 with the greater counter alternating current electromotive force, since the division of current between the circuits is determined not by the relative resistance of the circuits but bythecomparative counter 'electro-motive forces in the receiving circuits. In other words, when the new circuit 115, 115 is closed, 'the old circuit 114, 114 is robbed completely of its current flow. When,'h0wever, the current has become established. in the newly formed circuit 115, 115 the counter electromotive force of they alternating current rises, thus tending to reduce the ac- .tual flow of current, until the counter electromotive force approaches in value approximating the direct current supply. At or about this time a third circuit 116, 116 is closed in parallel with the second circuit 115,115, the first circuit 114, 114 having already been opened. This third circuit 116, 116 has for the moment a less alternating current counter electromotive force than the second circuit 115, 115. Current will then, in accordance with the above principle, be transferred from the second circuit 115, 115 to the third circuit 116, 116 and this circuit, in turn, Will be subjected to a rising counter electro-motive-force and the action goes on, each circuit turning over the current flow to another circuit having, for the instant, a lower counter electromotive force but later subjected to a rise of counter electromotive force in its turn in accordance with the normal progression of the system. The result then follows that the direct current voltage and current from the line, 2 are continuous in one circuit or another and always flow against the counter electromotive force of the alternating current of the synchronous machine, 27, and thus deliver power to that machine and that the substitution of one circuit for another is automatically made as the occasion requires.

It is understood that the rectifiers 5, 6, 7 8, 9, 10, 11, 12, 13, 14, 15, and 16 permit the passage of current in but one direction only, namely the direction toward the transformer primaries in the case of the odd numbered rectifiers and away from the transformer primaries in the case of the even numbered rectifiers, as shown in Fig. 1. These rectifiers are here illustrated as mercury vapor rectifiers, though I do not wish to limit myself to this particular form of rectifier, for other forms having the same property will serve equally well. I have also found these rectifiers to be especially suitable for high voltage Work. The polarity of the rectifiers shown will be maintained, if desired, by constituting the lower electrode a cathode and maintaining this electrode excited by any of the well known methods.

In order to resist any tendency for too rapid a change of potential in passing from one circuit to another and to maintain a relatively constant flow of current in the supply circuit I introduce reactances at various points, as shown in Fig. 1. The reactances 84 and 85 are very effectively placed for maintaining uniform current in the main line wire, while the reactances, 4, more particularly affect the rate of exchange of current from one branch circuit to another. This affects the wave form of the current in the transformer primaries. The adjustable inductances, 17, in series with these primaries further serve to control the wave form and steady the current flow. These various inductances can be mutually adjusted to produce almost any desired rate of interchange of current flow between circuits circuits. They also serve to prolong the period of current flow in any particular circuit for the transmission of a given amount of energy, considered with reference to a given cycle which works for better efficiency. These reactances also serve to control excessive rushes of current on the closing of new circuits with relatively low counter electromotive forces.

Having thus explained the interchange of power and current between the alternating current mains and the direct current line, I will describe the means used for establishing the frequency of the receiving circuit and for rendering automatic the adjustment ---of the flow of energy to the requirements of the circuit. 28 is a centrifugal governor driven from thesynchronous machine, 27, but controlling the field winding, 30, of the synchronous machine through the adjust ment of the resistance, 29, introduced between the supply battery, 31, and the generator.field, 30. If the speed of the syn: chronous machine exceeds a predetermined value, the governor cuts out resistance from the field circuit and strengthens the field magnetism which raises the voltage of the synchronous machine, 27, and thus cuts down the supply of current through the increasing of the counter electromotive force. This operation both controls the speed of the synchronous machine, 27, and then the fre quency of the circuit and automatically limits the flow of energy into the receiving system to the load requirements.

Fig. 2 shows a modification of Fig. 1 in which the circuits connecting the transformer windings with the direct current line are divided into two groups, those connecting the positive main with the transformer windings forming one group and those connecting the transformer windings to the negative main representing a second group. In Fig. 2 the transformer primaries areshown at 41, 42' and 43, the secondaries being shown at 41, 42 and 43, respectively.

- The transformer secondaries 41, 42 and 43 are-connected to the three alternating current mains 100, 101 and. 102 and the machine marked which is similarly connected and has a function similar to what is shown in Fig. 1 for the machine 27. The first group of circuits contain single phase rectifiers, having anodes connected to the positive direct. current line wire as shown at 46, 47,

48, 49, 50 and 51. Y The second group of circuits traverse a poly-phase rectifier 52,

havin six anodes and a single cathode. I

provi e' tvu) cylinders, each carrying a contact apparatus appropriate to one of the two roups of circuits, these two cylinders being own at A and B. As the operation-of the apparatusin. Fig. 2 is substantially thesame as that of Fig. 1, except for the'changes .06

sho n, A? 'reretit eaz of. the Mar t e thereof is required. It will be noted that brush 110, the transformer primary 41, the

right hand brush 107, the segment 107 the right hand brush 113, the rectifier 52 to the negative main. This generates an impulse in the transformer secondary 41 which is timed by the cylinder A and B to impart energy to the .machine (35 as explained in Fig. 1 for machine 27. At a certain later period energy flows from the supply main 2 to the rectifier 48 to the left hand brush 105, thQsegment 105, the left hand brush 111, the primary 42, the right hand brush 108, the segment 108", the right hand brush 114 to the rectifier 52 and the main 1, similarly for a subsequent current impulse for the transformer primary 43. A half cycle after the impulse through the transformer primary 43 currents enter the transformer 41 from the main 2 by, way of the rectifier 47, the right hand brush 104, the contact plate 104, the right hand brush 110, the transformer secondary 41 and continues through the left hand brush 107, the contact plate 107*, the left hand brush 113, the rectifier 52 and the main 1. Similarly for reverse impulses in the other transformer primaries. Thus in one complete cycle there occur six impulses of current from the supply passing through three transformers, two to a transformer, the two im ulses of the pair being oppositely directe These impulses are obviously all timed in synchronism with the similar impulses of the alternating voltage. maintained by the machine 65 in virtue of its continuous rotation.

In Figs. 2 and 2 are shown the extent of the circumference covered .by the several left hand contact plates on the surface of the cylinder A Fig. 2 and the right hand contact plates on the surface of the cylinder B Fig. 2. These contact plates may slightly overlap to give a continuous flow of current as already explained for Fig. 1. The left hand contact plates 104, 105 and 106 of the cylinder A and the right hand contact plates 107", 108 and 109 'of the cylinder B are placed 180 degrees around the cylinder from the like numbered contact -two groups of rectifiers and two switching cylinders are utilized. In this figure 1 and .2 are the direct current supply mains and 73, 74 and 75 are the receiving and distributiugtalternating current mains correspending to the mains 24, and 26 of Fig. 1. The conductor, 1*, acts as a positive direct main for the upper rectifying set 120 to 125, inclusive, and the conductor 2 acts as an operating negative direct current main for the lower set 120 to 125, inclusive, of rectifying rectifiers, these two conductors being connected as shown at 126 at the left of the figure. 65 is a three phase alternating current machine connected to the mains 73, 74 and 75 and having a neutral point of 1 the winding brought out and connected to the supplementary main, 114. Three transformer secondaries, 58, 59 and 60 are connected in delta across the three phase mains, 73, 74 and 75, and their high tension windings are shown at 55, 56 and 57. These high tension windings are connected through six leads 120*, 121", 122", 123*, 124" and 125", and six leads 120, 121, 122, 123, 124 and 125, withthe main 1, and 1 through a cylinder, 53, and the group of rectifier-s, 61, as in the system of Fig. 1. I have here illustrated the rectifiers merely by an arrow indicating the direction in which current is and 75 and all to the neutralbus bar, 114.

These transformer secondaries excite the corresponding windings, 79, and 81. These windings are connected to the direct current mains 2 and 2 through a switch cylinder, 64, as in the upper part of Fig. 3. The rectifiers,62, are introduced as above, and the, operation of the lower portion of the system will be understood to be similar to that of the upper.

Taking the system as a whole, direct current of the supply entersat the main, 2, and traverses the various circuits connected with the cylinder, 64, and the rectifiers, 62, and returns through the transformers 79,

80 and 81 to the main 2 and traverses this -tive forces of the transformer primaries,

55, 56 and 57 with the transformer primaries 79, 80' and 81 a very steady resultant electromotive force will be produced to balance the line direct current electromot-ivc force.

The change over from one branch circuit to another in the upper group of rectifiers occurs at a time intermediate between the changeover periods of the lower group of rectifiers.

I excite the machine, 65, with its field winding, 71, from the battery, 70, through the adjustable resistance, 69. I also suppl a supplemental field winding, 72, through the resistance, 68, by means of a commutator, 67, on the shaft of the machine, 65. This commutator, 67, is fed from the transformer, 66, which is fed from the windings of the machine, 65. Should, now, the voltage rise too high in the machine, 65, the voltage on the field would be raised by the supplemental field winding, 72, and the supply of energy to the system out down. This tends to maintain the voltage of the machine constant and thus with a constant setting of the resistance, 69. to maintain the speed of the machine and the ellicicncy constant. The regulating arrangement of Fig. 1 may also, if desired, be used in any of the ap 'ilications of my invention n'hcre approprlate.

The inductanccs 82 and 83 and the inductanccs 54 and the inductanecs 63 serve the purposes of the corresponding inductances in Fig. 1. Furthermore, if desired, inductances. can be used in series with the transformer primaries, 55. 56, 57, 79, 80 and 81. These inductanoes serve the function already explained in connection with the earlier figures.

The operation of the system of Fig. 3 in detail is as follows: Direct current of the supply enters at the main 2 and traverses the circuit 120, the elements 200, 200", 63, 62, 79, 62, 63, 200, 200 120 to the main 2 and traverses this to the main 1, the circuit 120', the elements 200", 200*, 61, 55, 61, 2200 200 the lead 120 to theoutgoing main 1. Current next flows from the main 2 through thecircuit 121, the elements 201, 201 63, 62, s0, 62, 63, 201 201 the lead 121 to the main 2, thence to the main 1, the circuit 121, the elements 201", 201*, 54, 61, 56, c1, 54, 201 201 the lead 121 to the outgoing main 1. The following impulse from the main 2 enters the circuit 122, the elements 202, 202, 63, 62, 81, 62, 63, 202, 202 the lead 122 to the negative main 2*, thence to the positive main 1, the lead 122, the elements 202*, 202, 54, 61, 57, 61, 54,202 202 the'lead 122 to the outgoing main 1. The next set of connections then comes into play and current flows from the main 2 by way of the lead 123, the elements 203, 203, 63, 62, 79, 62, 63, 203, 203, the lead 123* to the negative main 2' and the positive main 1 to the lead 123 the elements, 203', 203v, 54, 61, 55, 54,- 203, 203, the lead 123 to the outgoing main 1 Current next flows from the main 2 by the lead 125, the negative main 2, the positive main 1 tothe circuit 125', the elements 205 205%, 51, 61, 57, 61, 54, 205 205 and the lead 125.to the outgoing main 1. The

cyclical operation of all the sets of circuits will be clearly understood from what has already been said in connection with the other figures;

In Fig. 4, I show a system of circuits suitable for producing a high voltage direct current for supplying such receiving systems as have been shown 1n connection with the other figures of the drawings. At 80 I i show a three phase machine supplying three phase mains, 101, 102 and 103, and having a neutral point of the winding connected to a neutral main, 98. Two sets of transformer primaries, 87, 88 and 89, and 104, 105 and 106 are fed from this generator, the former three connected in star and the latter in delta. The transformer secondaries, 90, 91

and 92, and 107, 108 and 109 are supplied respectively from these primaries. These secondaries feed the rectifiers, 94, 95 and 96, and 110, 111 and 112, here. illustrated as mercury vapor rectifiers of the. usual type, the extremities of the windings being connected to two anodes and the middle points of the windings being connected,- some through reactances each to the cathode of a neighboring rectifier, the connection in the-case of the transformer secondary, 107, being through the transmission line and'the receiving circuits back to, the cathode of the rectifier, 96. I have shown these rectifiers as having metal cases and connect these cases to'the cathode through the conductors, 99. This serves to maintain the potential of the cases definite with respect to the portion of the circuit to which they are directly operated. If it is desirable this result may 7 be attained by connecting the case to any of the other leads or to points one of the windmgs with which ,the rectifier is directly .connected. .The inductance, 97, serves to steady the flow of current. Coils similar to 93 might be used wherever desired to steady current flow in the leads of thecathodes of the rectifiers 110, 111 and 112. The fact" that transformers delta connected have a phase difference of thirty degrees from transformers star connected to the same mains gives a very uniform and constant, electromotive force in the line wire fOI thIS is the summation of the six electromotive forces corresponding to the six transformers. I have now described one embodiment or one application of my invention, but I wish it understood that I do not consider it to be limited to this specific apparatus or method of operation for the principles I have used are of very broad application, and any use of them in connection with other appar'atus than that shown, either in whole or in part, comes within the scope of the present application. For example, although have shown three phase systems, four phase or any other number of phases might be used provided the arrangements are such of current to meet the particular requirements of any set of apparatus. In fact the transformers shown in the various figures may be omitted and the rectifier circuits connected directly to alternating current mains if the voltages are suitable. I may further recommend for certain classes of work the use of what might be called single phase re'ctifiers-in connection with the generator apparatus of Fig. 4, that is rectifiers having one main anode and one main cathode in each container with separate containers for each terminal of the supply. Again three phase transformers. or three phase groups ofjtransformers may be used in place of the single phase transformers and three phase rectifiers fed from three phase transformer secondaries may be then connected in series shown in Fig. .4.

I claim as my invention:

1. A. system 'of electrical distribution comprising a direct current transmission line, a receiving system containing a source of alternating current, and vapor rectifiers interposed between said transmission line and said receiving system, in combination with means for completing the circuits of said rectifiers, for passing .with regard to the direction of voltage in said alternating receiving system timed impulses to said reaccording to the system ceiving system, and for interrupting the cir- .cuit of said rectifier-s at othertimes, energy being thus supplied to said receiving parts in separate integral sections.

2. In a system of electrical distribution, a direct current supply source, a receiving circuit containing a source of alternating current, and means for controlling the direction of current between said direct ourrent'source and said receiving circuit, in combination with means for controlling the time .of current impulses from said supply to said receiving circuit.

3. In a system of electrical distribution a direct current supply circuit, a receiving circuit, an alternating current machine in said receiving circuit maintaining a definite frequency and rectifiers interposed between said direct current circuit and said machine in combination with circuit making and circuit breaking devices whereby energy is deternating voltage are in the same direction.

5. In a system of electrical distribution, the combination with a direct current source, a three phase alternating receiving circuit, three single phase transformers serving to raise the voltage in said receiving circuit and means for permitting the flow. of current from the direct current supply against elec tromotiv-eforce in any of said transformers "during periods of rising alternating voltage only in said transformer, of means for suppressing current flow 1n response to alternating voltage 1n said transformers operating in the same direction as in the direct source.

6. In a. system of electrical distribution, the combination with a direct current supply line, an alternatin receiving circuit, an alternating electromotive force machine in said circuit, means for permitting the voltage of the supply line to overcome the alternating voltage, thus causing the said alternating voltage to supply energy to said alternating system and means or raising said alternating voltage in response to an over supply of energy, whereby automatic adaptation of the supply of energy to the demands of the receiving circuit is obtained.

7. The combination with a direct current source, a dynamo electric machine capable of establishing an alternating electromotive force, means for'electrically impressing voltage from said direct current source upon said dynamo electric machine whereby en ergy is supplied thereto and means for determining the frequency established by said dynamo electric machine.

8. The combinatlon w1th a direct current source, a dynamo electnc machine capable of'establishing an alternating electromotive force, means for electrically impressing voltage from said direct current source upon said dynamo electric machine whereby energy is supplied thereto and means for determining the frequency established by said dynamo electric machine, said means including a centrifugal governor controlling the magnitude of the voltage of said dynamo electric machine. v y

9. In a system of electrical distribution, the combination with a direct current supply circuit, a receiving circuit, means for electrically passing impulses of current from said supply circuit in alternating directions upon said receiving circuit and means perated from said alternating impulses for establishing therefrom a definite alternating potential wave in said receiving circuit..

negative supply'wire and each transformer terminal, permitting a flow of current only in the direction from said transformer windings, circuit making and interrupting devices synchronously perated introduced between said supply mains and said rectifiers whereby a circuit is established between each transformer primary and the supply mains during periods of rising voltage in sald primary, said connection being made in such a direction that the electromotive force of the'supply and the momentary electromotive force of the transformer primary are opposed and means for maintaining the integrity of one set of connections until after the establishment of the next set of connectlons.

11. In a system of electrical distribution, a direct current supply circuit and three phase receiving circuit, three single phase transformers connected to the several phases of said three phase receiving circuit, a connection from each terminal of each transformer primary'to both mains of the direct current supply, a mercury vapor rectifier interposed in each connection from the positive supply main to a transformer terminal, permitting a flow of current only toward the transformer winding, a mercury vapor rectifier inserted in each connection between the negative supply wire and each transformer terminal, permitting a flow of current on y in he. direction ,frqm sai transformer winding, circuit making and interrupting devices synchronously operated introduced between said supplymains and said rectifiers whereby a circuit is established between each transformer primary and the supply mains during rising voltage in said primary, said connection being made in such a' direction that the electromotive force of the supply and the momentary electromotive force of the transformer winding are opposed and means for maintaining the integrity of one set of connec- V tions until after the establishment of the next set of connections, in combination with reactance coils in the several branch circuits containing said rectifiers.

- 12. In a system of electrical distribution, a 'direct current supply circuit and three phase receiving circuit, three single phase transformers connected to the several phases of said three phase receiving circuit, a connection from each terminal of each transformer primary to both mains of the direct current supply, a mercury vapor rectifier interposed in each connection from the positive supply main to. a transformer terminal, permitting a flow of current only toward the transformer winding,amercury vapor rectifier inserted in each connection between the negative supply wire and each transformer terminal, permitting a fiow of current only in the direction from said transformer winding, circuit making and interrupting devices synchronously operated introduced between said supply mains and said rectifiers whereby a circuit is established between each transformer primary and the supply mains during rising voltage in said primary, said connection being made in such a direction that the electromotive force of the supply and the momentary electromotive force of the transformer winding are opposed and means for maintaining the integrity of one set of connections, in combination with reactance coilsin the several branch'circuits containing said rectifiers and an inductance and a reactance in series with each transformer primary winding.

13. In a system of electrical distribution,

the combination with a direct current supply system and three transformer windings, means for exciting said windings from a three phase alternating receiving system, a. connection from the positive main of said supply circuit to each terminal of each transformer winding through a rectifier permitting the flow of current only in the direction toward the transformer winding, 9. rectifier provided with six anodes and a cathode, connections from said anodes to the terminals of said transformer windings and a connection from said cathode to the negative main of said supply circuit, a current switching device synchronously operated interposed between said transformer winding and said first named rectifier and a second synchronously operated switching device connected between said transformer windings and said last named rectifier, whereby a circuit is completed through each transformer only during periods of rising voltage in the said transformer in a direction opposed to the voltage of said supply system.

14. In a system of electrical distribution, a direct current supply system, a three phase alternating receiving circuit, a dynamo electric machine connected to the said circuit, three transformers connected in delta through rectifying devices to said supply system, three transformers connected in star to said receiving circuit and a second group of rectifiers, and circuit making and breaking devices whereby current from said direct current source is opposed through said first named group of transformers in a direction opposite to the alternating electromotive force of said transformers and afterward through said second group of transformers in a direction opposed to the electromotive forces in said second group of transformers.

Signed at New York, in the county of New York and State of New York, this 28th day of March, A. D. 1913.

PERCY H; THOMAS.

Witnesses:

HAROLD B. Woonwann, THOS. H. BROWN. 

